Clinicopathologic overlap of psoriasis, eczema, and psoriasiform dermatoses: A retrospective study of T helper type 2 and 17 subsets, interleukin 36, and β-defensin 2 in spongiotic psoriasiform dermatitis, sebopsoriasis, and tumor necrosis factor α inhibitor-associated dermatitis

Background: Thelper (Th) type 17 andTh2 cells mediatepsoriasis and eczema, respectively. Some dermatoses exhibit overlapping clinicopathologic features, and their immunopathology is relatively unexplored. Objective: To determine whether Th17 and Th2 subsets and interleukin (IL) 36 and beta-defensin 2 (BD-2) markers of IL-17 signaling expression can discriminate between biopsy samples of psoriasis and eczematous/spongiotic dermatitis and to use those markers to immunophenotype cases with clinicopathologic overlap. Methods: A retrospective study was performed on biopsy samples of psoriasis, eczema/spongiotic dermatitis, sebopsoriasis, tumor necrosis factor alpha inhibitor-associated psoriasiform dermatitis, and ambiguous cases diagnosed as spongiotic psoriasiform dermatitis. Dual CD4/GATA3 and CD4/RORC, IL-36, and BD-2 immunohistochemistry was performed. Results: IL-36 and BD-2 were strongly expressed in biopsy samples of psoriasis compared with eczema/spongiotic dermatitis. No significant differences were observed in the percentages of Th2 and Th17 cells between disease types. Strong expression of IL-36 and BD-2 was observed in a subset of spongiotic psoriasiform dermatitis, sebopsoriasis, and tumor necrosis factor alpha inhibitor-associated psoriasiform dermatitis biopsy samples. Limitations: This was an exploratory study with a small sample size. No multiple testing adjustment was done. Clinical follow-up was limited. Conclusions: In cases with clinicopathologic overlap between psoriasis and spongiotic dermatitis, IL-36, and to a lesser extent BD-2, may be used to assess for a psoriasis-like/IL-17 phenotype, which could inform therapeutic clinical decisions.